Conventionally, in the production of polyurethane resin aqueous dispersions, organic solvents have been used for decreasing viscosities. However, recently, the use of organic solvents has raised problems from the viewpoints of the flammability of organic solvents, the safety to the human body, the impact on the environment, etc. To cope with the problems, a method for producing a polyurethane resin aqueous dispersion without using an organic solvent has been proposed (for instance, JP-A-3(1991)-149214).
However, the polyurethane resin aqueous dispersion produced by the foregoing method contains many polyurethane resin particles having relatively large particle diameters. The particles tend to settle, and therefore, the foregoing material has a problem in storage stability.
It is an object of the present invention to provide a polyurethane resin aqueous dispersion having excellent storage stability.
It is another object of the present invention to provide an isocyanate group terminated prepolymer aqueous dispersion for achieving the above-described object.
It is still another object of the present invention to provide an isocyanate group terminated prepolymer aqueous dispersion and a polyurethane resin aqueous dispersion, which does not contain, or contains a small amount of, a surfactant and a solvent.
It is still another object of the present invention to provide a polyurethane resin sheet material, a paint, an adhesive, a tackiness agent, or a fiber-treating agent having less flammability, a high level of safety to the human body, and environmental friendliness.
It is still another object of the present invention to provide a polyurethane resin sheet material, a paint, an adhesive, a tackiness agent, or a fiber-treating agent possessing excellent waterproofness.
It is still another object of the present invention to provide a leather-like polyurethane resin sheet material in which resin migration is prevented.